Heavy metal ions have numerous adverse health effects due to their eco-toxic, carcinogenic and non-biodegradable nature. Detection of heavy metals using nanoparticle based sensors are typically based on monitoring changes in the properties of the nanoparticles, such as changes in surface plasmon resonance (SPR) absorptions, fluorescence, inter-nanoparticle interactions (ion-chelation-induced aggregation process), and others, upon binding of an analyte. These changes may be detected using absorption and fluorescence spectroscopy; however, they often require relatively larger sensor and analyte concentrations and may have anomalies due to ensemble averaging. Integration of chemosensors into a single particle sensory device would be an ideal prospect, as it increases the sensitivity of detection. Single particle sensors employed so far have disadvantages owing to difficulty in locating and distinguishing such particles with other impurities in the system as they may not have a unique shape. The limits of such detection systems have not extended beyond the femtomolar regime.